Method for manufacturing a multi-layer capacitor

ABSTRACT

A multi-layer capacitor is highly downsized and increased in capacity. A method for manufacturing the multi-layer capacitor includes, in the same vacuum chamber, forming a dielectric layer, treating a surface of the dielectric layer, forming a pattern in a metal electrode, forming the metal electrode on the dielectric layer, and treating a surface of the metal electrode. In this method, etching of the dielectric layer flattens a recessed part generated by an electrical insulation part.

FIELD OF THE INVENTION

The present invention relates to a multi-layer capacitor formed of adielectric layer and a metal thin film layer, and a method formanufacturing the capacitor.

BACKGROUND OF THE INVENTION

Recently, all electronic components including a capacitor have beenurgently required to be downsized and increased in performance. Capacityof the capacitor is proportional to an area of an electrode plate and isinversely proportional to a distance between electrodes. At this time, athickness of a dielectric is equal to the distance between theelectrodes. When dielectrics have the same dielectric constant, forincreasing capacity of the capacitor, the area of the electrode plateneeds to be increased or the dielectric layer needs to be thinned. Inother words, for downsizing the capacitor and simultaneously maintainingor increasing the capacity thereof, it is effective to thin thedielectric layer and increase an effective area of the electrode plate.As a laminated body that is formed of the dielectric layer and the metalthin film layer, and is used as a capacitor or the like, a filmcapacitor is known. Structure of the film capacitor is described below.A metal thin film made of aluminum or the like is firstly formed on aresin film during a vacuum deposition method or a sputtering method. Theresin film is made of polyester (for example, PEN or PET), polyolefin(for example, PP), or PPS. Metal thin films manufactured from such amethod are laminated or wound, thereby forming a film capacitor. Theresin film functions as a dielectric. In this case, constraint inmanufacturing the film limits thinning of the resin film. A minimumthickness of a film for a presently used film capacitor is about 1.2 μm.For further increasing capacity of the capacitor, an effective area ofthe dielectric needs to be increased, namely a number of laminations anda number of turns need to be increased. However, simultaneous downsizingand capacity increase of the film capacitor causes a limit to bereached. U.S. Pat. No. 5,125,138 discloses a multi-layer capacitor inwhich a laminated body is formed of a dielectric layer and a metal thinfilm layer, with a thickness of the dielectric layer being about 1 μm.The dielectric layer is formed by polymerizing a reactive monomer.Japanese Patent Unexamined Publication No. H11-147279 discloses a chipcapacitor having a dielectric layer formed by polymerizing a reactivemonomer. FIG. 6 is a sectional view showing a structure of aconventional multi-layer chip capacitor.

In FIG. 6, internal electrodes 11 and dielectric layers 12 aresequentially laminated, and electrical insulation part 13 exists in eachinternal electrode 11 every two layers. External electrodes 41 arefinally formed to constitute a multi-layer chip capacitor as a product.Electrical insulation parts 13 are provided for forming a capacitor.Electrical insulation parts 13 function for preventing a short circuitand increasing an effective area of dielectrics in a capacitor formingpart.

Electrical insulation parts 13 have no metal layer, so that uneven partsoccur in the capacitor in response to an increase of a number of layers.This state is shown in the enlarged view of electrical insulation parts13 of FIG. 7. When the number of layers exceeds 1000, electricalinsulation parts 13 can be deeply recessed as shown in FIG. 8. In such acase, each internal electrode 11 is disconnected or internal electrodes11 are short-circuited, thereby damaging function as a capacitor. Thisproblem can be further noticeable when a thickness of the dielectriclayers is decreased to a thickness unachievable in a conventional filmcapacitor. The present invention aims to essentially address the problemoccurring in achieving downsizing or high capacity of a capacitor. Animprovement of productivity is also one purpose of the presentinvention.

SUMMARY OF THE INVENTION

The present invention provides a multi-layer capacitor in which aplurality of dielectric layers and metal electrode layers aresequentially laminated. Metal electrode layers alternately have anelectrical insulation part. The dielectric layers cover and flattenrecessed parts in the metal electrode layers produced by the electricalinsulation parts.

The present invention provides a method of manufacturing the multi-layercapacitor. The method comprises the following:

a monomer deposition process of forming a dielectric layer on a surfaceof a can roller rotating in a constant direction in a vacuum chamber;

a patterning process of supplying patterning material to a part of thedielectric layer that corresponds to an electrical insulation part andlies on a surface of the dielectric layer, and forming the electricalinsulation part;

a metal deposition process of forming a metal electrode layer on asurface of the dielectric layer except for the electrical insulationpart; and

a flattening process of flattening a recessed part generated by theelectrical insulation part of a laminated body that is formed byrepeating the procedures discussed above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a manufacturing apparatus of a multi-layer capacitor of thepresent invention.

FIG. 2A to FIG. 2C show a manufacturing process in accordance withexemplary embodiment 1 of the present invention.

FIG. 3A to FIG. 3C show a manufacturing process in accordance withexemplary embodiment 2 of the present invention.

FIG. 4A to FIG. 4C show a manufacturing process in accordance withexemplary embodiment 3 of the present invention.

FIG. 5 is a sectional view illustrating a form having differentlaminating positions of the present invention.

FIG. 6 is a sectional view illustrating a structure of a conventionalmulti-layer capacitor.

FIG. 7 is a sectional view illustrating an enlarged electricalinsulation part of the conventional multi-layer capacitor.

FIG. 8 is a perspective view illustrating an electrical insulation partof the conventional multi-layer capacitor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of the present invention will be hereinafterdescribed with reference to the accompanying drawings. The accompanyingdrawings are pattern diagrams and do not show respective positions inaccurate size.

FIG. 1 shows a manufacturing apparatus of a multi-layer capacitor of thepresent invention. Metal deposition source 4 is disposed under canroller 1 that rotates in the arrow direction in FIG. 1 at a constantangular velocity or a constant circular velocity. Metal electrodesurface treating unit 7, monomer evaporation source 2, curing unit 8,resin surface treating unit 9, and patterning material supplying unit 3are disposed sequentially in a rotational direction of can roller 1 froma downside thereof. These units are engaged with vacuum chamber 5, andan interior of the chamber is maintained in a vacuum via vacuum pump 6.An outer peripheral surface of can roller 1 is finished smoothly andspecularly, and preferably cooled to −20 to 40° C., especiallypreferably to −10 to 10° C. A rotational speed can be set arbitrarily,but is preferably within a range of 15 to 70 rpm. Metal depositionsource 4 has a shutter (not shown) facing the outer peripheral surfaceof can roller 1 so as to control an interval of metal deposition. Ametal electrode layer is thus formed on a surface of a dielectric layer.As the metal for the deposition, at least one selected from a group ofAl, Cu, Zn, Sn, Au, Ag, and Pt, for example, is employed. This metalelectrode may be formed via a sputtering method or the like instead of avacuum deposition method. Metal electrode surface treating unit 7performs an improving treatment of adhesiveness between a metalelectrode surface and a dielectric resin layer. For example, titaniumatoms are deposited on a metal electrode surface during the sputteringmethod or the vacuum deposition method. A chemical bond of metal(electrode)-Ti-carbon (resin) is formed as a result.

Adhesiveness between resin and metal can be thus improved. A similareffect can be obtained also via a chemical vapor deposition (CVD) methodusing TiCl₄ or the like as raw material. When coupling material is addedto the metal electrode, the coupling material segregates on an interfacebetween the metal and the dielectric with heat treatment performedduring a subsequent process of forming a laminated body. A chemical bondsimilar to that discussed above can therefore be obtained andadhesiveness can be improved. When light energy equivalent topolymerizing energy of a reactive monomer is radiated, bonding of apolymerization starting part is broken and a chemical bond ofmetal—carbon (resin component) is formed. An effect similar to that in acase where the coupling material is deposited on the metal surface cantherefore be obtained. Monomer evaporation source 2 evaporates andvaporizes a reactive monomer toward the outer peripheral surface of canroller 1. A shutter (not shown) is disposed so as to control adeposition interval of the reactive monomer onto can roller 1. Thereactive monomer is deposited, and finally a dielectric layer is formed.This deposited reactive monomer is polymerized or cross-linked by curingunit 8 to form a resin thin film having a desired degree of cure. Apolymerization initiator can be used additionally if necessary. Ascuring unit 8, for example, a radiating device of electron beams orultraviolet rays is used. A resin thin film cured by curing unit 8 issurface-treated by resin surface treating unit 9. For example, an oxygenplasma treatment or the like activates a resin surface. Adhesiveness tothe metal thin film can therefore be improved. Patterning materialsupplying unit 3 deposits patterning material onto a surface of theresin thin film in a band shape. No metal thin film is formed in a placehaving deposited patterning material, and this place forms an electricalinsulation part in the laminated body. A laminating position of theelectrical insulation part is preferably displaced from a laminatingposition of an electrical insulation part in an adjacent layer unit. Asthe patterning material, for example, oil or paraffin can be employed.For supplying the patterning material, it is preferable to use a methodof jetting evaporated and vaporized patterning material from a nozzleand liquefying it on the surface of the resin thin film. A predeterminednumber of layers including the resin layer and the metal layer arelaminated onto the outer peripheral surface of can roller 1, in themethod discussed above. Here, the metal layer is laminated onto a partother than a band-like electrical insulation part. A cylindricalcontinuous body is thus formed. The continuous body is radially divided,for example, into eight parts every 45°, and removed from the canroller. Each divided body is then heated and pressed, thereby providinga flat parent element of the laminated body. The parent element is thencut to provide a laminated body in accordance with the manufacturingmethod of the present invention. According to the method discussedabove, a laminated body can be manufactured efficiently andinexpensively by a simple method.

(Exemplary Embodiment 1)

The manufacturing apparatus shown in FIG. 1 is used in exemplaryembodiment 1. FIG. 2A to FIG. 2C show a manufacturing process of amulti-layer capacitor of the present invention. Degree of vacuum invacuum chamber 5 is set at 2×10⁻² Pa. The outer peripheral surface ofcan roller 1 is kept at 5° C. Dicyclopentadiene dimethanol diacrylate isused as a reactive monomer forming dielectric material. This isvaporized by monomer evaporation source 2 and deposited onto the outerperipheral surface of can roller 1. As the reactive monomer, arbitrarymaterial that is easily deposited and forms a good thin film afterpolymerization may be used. Polyfinctional acrylate, polyfinctionalmethacrylate, or polyfunctional vinyl ether is preferable.

Next, an electron-beam radiating device is used as curing unit 8, andcures deposited dielectric material. At this time, a thickness of aformed dielectric layer 12 is 0.1 μm. Resin surface treating unit 9 thenapplies an oxygen plasma treatment to a surface of dielectric layer 12.Patterning material supplying unit 3 supplies a patterning material to apart corresponding to electrical insulation parts 13. Fluorine-base oilis used as the patterning material. The patterning material isvaporized, jetted from a nozzle having a diameter of 50 μm, and adheredto the surface of dielectric layer 12 in a 150 μm-wide band shape. Metaldeposition source 4 then deposits aluminum for forming internalelectrode 11. Thickness of this deposited layer is 25 nm, and a surfaceresistance thereof is 6 Ω/square. Metal electrode surface treating unit7 then deposits titanium to a 0.1 nm thickness during a sputteringmethod. The operations discussed above are repeated 3000 times byrotating can roller 1. The process until now is called process A. FIG.2A shows a state at completion of process A. Next, a procedure offlattening electrical insulation recessed part 14 is described.Electrical insulation recessed part 14 is shown by a broken line. Sincethe recessed part is formed of dielectric material, the broken line isused for distinguishing between the dielectric materials. Metaldeposition source 4 is firstly partitioned by a shutter, and monomerevaporation source 2 and curing unit 8 form resin layer 15 by repeatinglamination and curing about 500 to 1000 times. Monomer evaporationsource 2 is then partitioned by a partition plate. Resin surfacetreating unit 9 etches resin layer 15 with oxygen plasma as shown inFIG. 2B. Electrical insulation recessed part 14 is thus filled toflatten a surface of the laminated body as shown in FIG. 2C. Repeatingthe operations discussed above forms a laminated body having a thicknessof about 1.6 mm. An obtained cylindrical laminated body is then radiallydivided into twenty pieces and removed. A flat parent element of thelaminated body is obtained by performing a hot pressing operation. Thiselement is cut, and then forms a chip capacitor as a product in aprocess similar to that for a conventional film capacitor. This processincludes installation of an external electrode, for example. Thisobtained chip capacitor has a thickness of 1.3 mm in a laminateddirection, depth of 1.6 mm, and width of 3.2 mm (the direction betweenboth external electrodes). This chip capacitor is small, but has 4.7 μFof capacity and 6.3 V of withstand voltage. The chip capacitor ismounted to a printed wiring board via solder. Any problem such asbreakage of the laminated body or degradation of a capacitorcharacteristic does not occur.

(Exemplary Embodiment 2)

A capacitor of exemplary embodiment 2 is manufactured using theapparatus shown in FIG. 1 in the same method as that of exemplaryembodiment 1 until process A is completed. FIG. 3A shows a state atcompletion of process A. A procedure of flattening electrical insulationrecessed part 14 is described. Metal deposition source 4 is firstlypartitioned by a shutter, and monomer evaporation source 2 and curingunit 8 form resin layer 21 by repeating lamination and curing about 500to 1000 times. Monomer evaporation source 2 is then partitioned by ashutter, and resin surface treating unit 9 applies argon plasma to resinlayer 21 as shown in FIG. 3B. At this time, a corner of a recessed partof resin layer 21 is firstly ground selectively, and finally resin layer21 can fill the recessed part in its entirety. A surface of thislaminated body can be flattened as shown in FIG. 3C. Argon is used asinert gas in the present embodiment; however, another inert gas such asxenon or neon may be used.

Repeating the operations discussed above forms a laminated body having athickness of about 1.6 mm. A chip capacitor is obtained from thelaminated body similarly to embodiment 1. This chip capacitor has acapacitor characteristic and solder heat resistance similar to those inembodiment 1.

(Exemplary Embodiment 3)

A capacitor of exemplary embodiment 3 is manufactured using theapparatus shown in FIG. 1 in the same method as that of exemplaryembodiment 1 until process A is completed. FIG. 4A shows a state atcompletion of process A. A procedure of flattening electrical insulationrecessed part 14 is described. Monomer evaporation source 2 is firstlypartitioned by a shutter, and metal deposition source 4 is partitionedby shutter 31 having a pattern part. Metal layer 32 is passed throughthe pattern part and laminated about 500 to 1000 times, as shown in FIG.4B. Metal layer 32 fills the recessed part generated by the electricalinsulation part and flattens a surface of the laminated body, as shownin FIG. 4C. Repeating the operations discussed above forms a laminatedbody of about 1.6 mm. A chip capacitor is obtained from the laminatedbody similarly to embodiment 1. This chip capacitor has a capacitorcharacteristic and solder heat resistance similar to those inembodiment 1. In embodiments 1 to 3, a laminating position of theelectrical insulation part is the same as a laminating position of anelectrical insulation part in an adjacent layer. However, it ispreferable that laminating positions of the electrical insulation partsin adjacent layers do not overlap as shown in FIG. 5. More preferably,lamination is performed while periodically changing laminationpositions. The laminating positions of the electrical insulation partsin the adjacent layers are set different from each other, therebyreducing unevenness generated by the electrical insulation parts. Thus,disconnection of an internal electrode and occurrence of a short circuitcan be prevented. In embodiments 1 and 2, a thickly laminated dielectriclayer is etched to flatten the surface of the laminated body. Anothermethod such as laser ablation, namely a method of physically evaporatingthe surface of the laminated body, can be also used. A combination ofthese methods can be also used. A degree of flattening in the presentinvention is required to be simply enough to prevent disconnection ofinternal electrode 11 or a short circuit between layers from beingcaused by deep recessing of electrical insulation part 13. The presentinvention provides a manufacturing method allowing improvement ofproduct yield of a small multi-layer capacitor having high capacity.

1. A method for manufacturing a multi-layer capacitor comprising: in thesame vacuum chamber (a) depositing a monomer onto a rotating can rollerso as to form a dielectric layer on a surface of said can roller; (b)supplying a patterning material onto a part of a surface of saiddielectric layer so as to form an electrical insulation part; (c)depositing a metal onto said surface of said dielectric layer, but notonto said electrical insulation part, so as to form a metal electrodelayer; (d) repeating (a), (b) and (c) so as to form a laminated bodyhaving a recessed part corresponding to the electrical insulation parts;and (e) flattening said recessed part, wherein depositing the monomeronto the rotating can roller comprises operating a shutter to open andclose an opening through which said monomer passes from a monomersource, so as to control an interval of time during which said monomeris deposited onto said rotating can roller.
 2. The method according toclaim 1, wherein repeating (a), (b) and (c) so as to form the laminatedbody comprises repeating (a), (b) and (c) so as to form a cylindricallaminated body, and further comprising: dividing said cylindricallaminated body into individual segments; removing said individualsegments from said can roller; hot pressing said individual segments soas to obtain flat laminated bodies; and cutting said flat laminatedbodies into chip capacitors.
 3. A method for manufacturing a multi-layercapacitor comprising: in the same vacuum chamber (a) depositing amonomer onto a rotating can roller so as to form a dielectric layer on asurface of said can roller; (b) supplying a patterning material onto apart of a surface of said dielectric layer so as to form an electricalinsulation part; (c) depositing a metal onto said surface of saiddielectric layer, but not onto said electrical insulation part, so as toform a metal electrode layer; (d) repeating (a), (b) and (c) so as toform a laminated body having a recessed part corresponding to theelectrical insulation parts; and (e) flattening said recessed part,wherein depositing the metal onto said surface of said dielectric layercomprises operating a shutter to open and close an opening through whichsaid metal passes from a metal source, so as to control an interval oftime during which said metal is deposited onto said dielectric layer. 4.The method according to claim 3, wherein repeating (a), (b) and (c) soas to form the laminated body comprises repeating (a), (b) and (c) so asto form a cylindrical laminated body, and further comprising: dividingsaid cylindrical laminated body into individual segments; removing saidindividual segments from said can roller; hot pressing said individualsegments so as to obtain flat laminated bodies; and cutting said flatlaminated bodies into chip capacitors.
 5. A method for manufacturing amulti-layer capacitor comprising: in the same vacuum chamber (a)depositing a monomer onto a rotating can roller so as to form adielectric layer on a surface of said can roller; (b) supplying apatterning material onto a part of a surface of said dielectric layer soas to form an electrical insulation part; (c) depositing a metal ontosaid surface of said dielectric layer, but not onto said electricalinsulation part, so as to form a metal electrode layer; (d) repeating(a), (b) and (c) so as to form a laminated body having a recessed partcorresponding to the electrical insulation parts; and (e) flatteningsaid recessed part; depositing a reactive monomer onto said laminatedbody and then curing said reactive monomer so as to form a thin resinfilm on said laminated body; and activating said thin resin film byperforming a surface treatment thereon, wherein activating said thinresin film by performing the surface treatment thereon comprises etchingsaid thin resin film with oxygen plasma, and wherein flattening saidrecessed part comprises the etching of said thin resin film with oxygenplasma.
 6. The method according to claim 5, wherein repeating (a), (b)and (c) so as to form the laminated body comprises repeating (a), (b)and (c) so as to form a cylindrical laminated body, and furthercomprising: dividing said cylindrical laminated body into individualsegments; removing said individual segments from said can roller; hotpressing said individual segments so as to obtain flat laminated bodies;and cutting said flat laminated bodies into chip capacitors.
 7. A methodfor manufacturing a multi-layer capacitor comprising: in the same vacuumchamber (a) depositing a monomer onto a rotating can roller so as toform a dielectric layer on a surface of said can roller; (b) supplying apatterning material onto a part of a surface of said dielectric layer soas to form an electrical insulation part; (c) depositing a metal ontosaid surface of said dielectric layer, but not onto said electricalinsulation part, so as to form a metal electrode layer; (d) repeating(a), (b) and (c) so as to form a laminated body having a recessed partcorrespondings to the electrical insulation parts; and (e) flatteningsaid recessed part, wherein flattening said recessed part comprisesfilling said recessed part by subjecting a thin resin film on saidlaminated body to plasma of a gas.
 8. The method according to claim 7,wherein subjecting the thin resin film on said laminated body to plasmaof the gas comprises subjecting said thin resin film to plasma of anoxygen gas.
 9. The method according to claim 8, wherein repeating (a),(b) and (c) so as to form the laminated body comprises repeating (a),(b) and (c) so as to form a cylindrical laminated body, and furthercomprising: dividing said cylindrical laminated body into individualsegments; removing said individual segments from said can roller; hotpressing said individual segments so as to obtain flat laminated bodies;and cutting said flat laminated bodies into chip capacitors.
 10. Themethod according to claim 7, wherein subjecting the thin resin film onsaid laminated body to plasma of the gas comprises subjecting said thinresin film to plasma of an inert gas.
 11. The method according to claim10, wherein subjecting said thin resin film to plasma of the inert gascomprises subjecting said thin resin film to plasma of at least oneinert gas selected from the group consisting of argon, xenon and neon.12. The method according to claim 11, wherein repeating (a), (b) and (c)so as to form the laminated body comprises repeating (a), (b) and (c) soas to form a cylindrical laminated body, and further comprising:dividing said cylindrical laminated body into individual segments;removing said individual segments from said can roller; hot pressingsaid individual segments so as to obtain flat laminated bodies; andcutting said flat laminated bodies into chip capacitors.
 13. The methodaccording to claim 10, wherein repeating (a), (b) and (c) so as to formthe laminated body comprises repeating (a), (b) and (c) so as to form acylindrical laminated body, and further comprising: dividing saidcylindrical laminated body into individual segments; removing saidindividual segments from said can roller; hot pressing said individualsegments so as to obtain flat laminated bodies; and cutting said flatlaminated bodies into chip capacitors.
 14. The method according to claim7, wherein repeating (a), (b) and (c) so as to form the laminated bodycomprises repeating (a), (b) and (c) so as to form a cylindricallaminated body, and further comprising: dividing said cylindricallaminated body into individual segments; removing said individualsegments from said can roller; hot pressing said individual segments soas to obtain flat laminated bodies; and cutting said flat laminatedbodies into chip capacitors.
 15. A method for manufacturing amulti-layer capacitor comprising: in the same vacuum chamber (a)depositing a monomer onto a rotating can roller so as to form adielectric layer on a surface of said can roller; (b) supplying apatterning material onto a part of a surface of said dielectric layer soas to form an electrical insulation part; (c) depositing a metal ontosaid surface of said dielectric layer, but not onto said electricalinsulation part, so as to form a metal electrode layer; (d) repeating(a), (b) and (c) so as to form a laminated body having a recessed partcorresponding to the electrical insulation parts; and (e) flatteningsaid recessed part, wherein flattening said recessed part comprisesfilling said recessed part with metal that passes through a pattern partof a shutter positioned between said recessed part and a metaldeposition source.
 16. The method according to claim 15, whereinrepeating (a), (b) and (c) so as to form the laminated body comprisesrepeating (a), (b) and (c) so as to form a cylindrical laminated body,and further comprising: dividing said cylindrical laminated body intoindividual segments; removing said individual segments from said canroller; hot pressing said individual segments so as to obtain flatlaminated bodies; and cutting said flat laminated bodies into chipcapacitors.